Regulation of a patient's body temperature as a result of surgery, heat prostration, hypothermia, or other conditions, is often required. Heat transfer blankets or covers, such as those disclosed in U.S. Pat. No. 2,110,022 (Kleisrath), have been suggested wherein a heat transfer fluid is circulated throughout a composite fabric in coils or conduits disposed throughout the fabric or quilt matrix. For example, in the '022 patent disclosure, the coils wind through a composite fabric composed of a wool blanket top layer and a heat conducting blanket layer formed from cotton, linen, silk, etc.
In another embodiment of U.S. Pat. No. 2,110,022, a woolen blanket upper layer is disposed over a bag formed from rubber or similar flexible material. Cooling air is forced into the bag and exits over the patient through a plurality of discrete openings in the bottom bag side.
Another airflow device is disclosed in U.S. Pat. No. 4,572,188 (Augustine et al) wherein the airflow cover comprises a parallel array of longitudinally arranged, inflatable, plastic tubes that are joined together along lengthwise sides. Transverse, connecting channels are provided in the tubes so that a thermally controlled gas mixture introduced through an entry port, fills the tubes and exits over the patient through a series of exit ports on the flattened bottom side of the tube array.
As sold commercially, the manufacturer of the '188 device suggests that it be used in combination with an overlying surgical drape. Moreover, due to the plurality of discrete openings in the bottom flattened portions of the parallel plastic tubes, air emanating from the tubes jets across the patient at a plurality of distinct locations in contradistinction to uniform and gentle diffusion of the heating (or cooling) medium over the entirety of the covered surface.
Another approach to the problem is disclosed in U.S. Pat. No. 5,044,364 (Crowther). In this device, a plurality of arch-shaped air pockets are provided 9 transversely spanning the treated patient. Openings between adjacent air pockets allow inflation air to flow from one pocket to the next until the pockets are fully inflated. A separate air chamber is disposed underneath the transverse arch-shaped pockets and is provided with a plurality of perforations therein allowing air to flow continuously over the treated patient.